Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “D_dyn”

Abstract

[1] During magnetic storms, wind disturbances produced by auroral phenomena can affect the whole thermospheric circulation and associated ionospheric dynamo currents for many hours after the end of the storms. In this paper we define criteria to select a new simple type of ionospheric disturbance dynamo events that allow a simple interpretation over all longitude sectors. These events exhibit a weak auroral activity during at least 24 UT hours, on the day after the storm. We analyze the magnetic disturbances ''D dyn '' observed at equatorial latitudes in the three longitude sectors of such selected events. It is found for all the cases that the amplitude of the H component of the Earth's magnetic field is reduced, on the day after storm at equatorial latitudes, in agreement with the ionospheric disturbance dynamo model (Blanc and Richmond, 1980). The observation of H component decrease on the day after storm is longitudinally asymmetric. The observed signature of the ionospheric disturbance dynamo process in a specific longitude sector is strongly dependent on the magnitude, the start time, and the duration of the storm.Citation: Le Huy, M., and C. Amory-Mazaudier (2005), Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: ''D dyn '',

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

“…The effect of the disturbance dynamo reduces or sometimes even reverses the eastward electric field produced by normal quiet-time winds. The disturbance dynamo electric field can persist for several days after geomagnetic activity quiets down, and thus can result in a reduced EEJ or CEJ during the recovery phase of a storm (Le Huy and Amory-Mazaudier 2005;. More discussion on the storm-time response of Sq and EEJ can be found in Sect.…”

“…The westward disturbance winds, and thus the electrodynamic disturbances, can persist for many hours after the high-latitude energy input ceases (Huang et al 2005a(Huang et al , 2005b. Accordingly, the disturbance dynamo effects are often detected during the recovery phase of a storm (e.g., Le Huy and Amory-Mazaudier 2005;Zaka et al 2009;.…”

Latitudinal profile of the ionospheric disturbance dynamo magnetic signature: comparison with the DP2 magnetic disturbance

“…In 1980, Blanc and Richmond observed the electric field disturbance, after the end of a storm, due to the dynamo action of storm thermospheric winds generated by auroral Joule heating, during the active phases of the storm and first proposed the ionospheric disturbance dynamo mechanism to explain this phenomenon (Fejer et al, 1983;Sastri, 1988;Fambitakoye et al, 1990;Mazaudier and Venkateswaran, 1990;Fejer and Scherliess, 1995;Fejer, 2002). The limited number of studies related to the disturbance dynamo mechanism, from the time of the work of Blanc and Richmond (1980) to those of Le Huy and Amory- Mazaudier (2005), confirm the complexity of the attempt to isolate ionospheric disturbed dynamo events. Although storm time ionospheric electric fields and currents have been investigated extensively, there are still some fundamental difficulties in understanding their signatures and driving mechanisms (Fejer et al, 1990).…”

“…The recent studies on the Ddyn disturbance marked some progresses in Published by Copernicus Publications on behalf of the European Geosciences Union. the understanding of its mechanism including the definition of the criteria of identifying such events (Richmond et al, 2003;Sastri et al, 2003;Le Huy and Amory-Mazaudier, 2005). A comparison between latitudinal variations of the Ddyn disturbance and the direct penetration mechanisms has not been established yet.…”

“…In this report, we used 1-min digital magnetometer data recorded at high, middle and equatorial latitudes to select Ddyn events through case studies. We carry out a comparative study of the dayside latitudinal profiles of the Ddyn disturbance magnetic signature (Le Huy and Amory-Mazaudier, 2005) and the magnetic disturbance due to the ionospheric currents generated by the magnetospheric convection electric field (Nishida et al, 1966;Nishida, 1968).…”